Proceedings of the 11th International Conference and 32nd Annual General Meeting of the Nigerian Institution of Agricultural Engineers (NIAE Ilorin 2011), October 17 – 20, 2011, Ilorin, Nigeria. ISBN: 978-036-578-8 Coconut Husk Ash as a Partial Replacement of Cement in Sandcrete Block Production Oyelade, O. A. (2011). Vol. 32: 465 – 469.
Coconut Husk Ash as a Partial Replacement of Cement in Sandcrete Block Production Oyelade, Olumide Akintoye Civil Engineering and Environmental Department, University of Lagos Nigeria Abstract The urge to find alternative materials to existing conventional ones and the need to improve the strength of sandcrete blocks have compelled researchers to intensify work on substitutes to cement with a view to investigating their usefulness wholly as a construction material or partly as a substitute for cement in sandcrete blocks. This project investigates the possible use of coconut husk ash (CHA) as a partial replacement of cement in sandcrete block production. 140 numbers of 450mmx150mm×225mm hollow sandcrete blocks of mix ratio 1:8 were cast, cured and crushed at 7, 14, 21, and 28 days. The coconut husk ash was replaced at 0 to 30 percent levels at 5% intervals. The maximum compressive strength of 2.10 N/mm2 was recorded at 5% replacement at 28th day. The compressive strength of the ordinary Portland cement /coconut husk ash sandcrete blocks generally decreases as the percentage of coconut husk ash content increases. The maximum value of 2.10N/mm2 for the 5% replacement level is found suitable and recommended for building construction having attained a 28-day compressive strength of more than 2.0N/mm2 as required by the Nigeria National Building Code (2006) for non load bearing walls. Keywords: coconut husk ash, sandcrete, replacement, compressive strength. 1. Introduction Sandcrete blocks are composite material made up of cement, sand and water, moulded into different sizes. It is widely used in Nigeria and other countries like Ghana, Ireland as walling unit. The quality of blocks produced however, differs from each industry due to the different methods employed in the production and the properties of the constituent materials. The importance of the blocks as part of local building materials cannot be over emphasized in building and construction industry. Sandcrete blocks have been widely used for building construction in Nigeria. However it is observed that clay suitable for making high strength bricks are not available in every place in Nigeria and the clay bricks produced and presently used in construction are not uniform in quality. The rapid changes in the use of brick to block in Nigeria have encouraged the investigations into the use of sandcrete blocks to be more elaborate. It was also realised that some places in Ondo and Ekiti States in Nigeria were occupied by rivers, which make it easier to obtain river sand rather than clay for making blocks. Also in Minna communities, sand is easily obtained from borrow pits and riverbeds situated in the environment which enhance the use of sand for block making (Abdullahi, 2005). Oyekan (2008) carried out work on the use of sawdust and sugar as admixtures in sandcrete blocks production. He discovered that sawdust as an air entraining agents has no appreciable effect on the compressive strength of blocks. The result on the use of sugar showed that sugar had a significant effect on the compressive strength of the blocks increasing it by 17% at 28 days. Nimityongskul and Daladar (1995) conducted an experiment to develop new kinds of pozzolana from other agricultural wastes apart from rice husk and rice straw. The study investigated the use of coconut husk, corn cob and peanut shell ash as cement replacement materials. A series of tests were performed to determine the chemical composition of coconut husk ash, corn cob ash and peanut shell ash which are referred to as CHA, CCA and PSA respectively. The mechanical properties of paste and mortar containing different percentages of ash replacement were investigated. Experimental results revealed that coconut husk ash and corn cob ash cannot be utilized as pozzolana while peanut shell ash is classified as Class C pozzolana according to ASTM Standards. Oyekan (2007) investigated the strength characteristics of sandcrete blocks in which crushed waste glass is partially replaced with cement in sandcrete block production. Crushed waste glass was discovered to have significant effect on the compressive strength of sandcrete blocks. At a mix proportion of 1:6 the compressive strength of the 450mm x 150mm x 225mm blocks (at 28 days) increased by 39% over the control value and by nearly 74% over the control value for the 450mm x 225mm x 225mm blocks. 2. Materials used and Manufacture of Sandcrete Blocks 2.1 Materials
2.1.1 Sand
465
Coconut Husk Ash as a Partial Replacement of Cement in Sandcrete Block Production Oyelade, O. A. (2011). Vol. 32: 465 – 469.
The Sand used was clean, sharp river sand that was free from clay. The sand had a specific gravity of 2.60. 2.1.2 Cement The cement used was ordinary Portland cement from the West African cement company, Ewekoro in Ogun State, Nigeria with properties conforming to BS 12(1971). The properties of the cement are shown in Table 1. 2.1.3 Water The water used was potable, fresh, colourless, odourless and tasteless water that is free from organic matter of any type. 2.1.4 Coconut Husk Ash (CHA) The coconut husk for this research was collected from Badagry in Lagos State. 75 bags were collected for burning. The burning was done in the gas kiln of Federal Institute Industrial Research Oshodi (FIIRO) in Oshodi, Lagos Nigeria. The 75 bags were loaded into the gas kiln gradually for 3 days. Chemical analysis of CHA was carried out in the laboratory of Chemistry Department of University of Lagos, Nigeria. The properties are shown in Table 1. 2.2 Manufacture of Sandcrete Blocks In this study, the hollow blocks were manufactured with the use of the fabricating machine. One mix proportion of 1:8 was used in the production of 450mm x 225mm x 225mm sandcrete block. One hundred and forty of 450mmx150mmx225mm hollow sandcrete blocks were produced. The quantities of materials obtained from the mix design were measured in each case by volume. The percentage of CHA content was varied in steps of 5% to a maximum of 30%. For the experiment, hand mixing was employed, and the materials were turned over a number of times until an even colour and consistency was attained. Water was then added as required through a fire hose, and the materials were further turned over to secure adhesion. It was then rammed into the machine mould, compacted and smoothened off with a steel face tool. After removal from the machine moulds, the blocks were left on pallets under cover and kept wet by watering through a fine watering hose. Testing for crushing strength was then carried out at 7, 14, 21 and 28 days. 3. Results and Discussion The results are presented in tabular and graphical forms. Table 2 shows the results of the compressive strength test at various percentages of CHA contents. Figure 1 shows the plot of compressive strength against percentage CHA content at ages 7, 14, 21 and 28 days. Figure 2 shows the plot of dry density against percentage of CHA contents. 3.1 Effect of Coconut Husk Ash on Compressive Strength The compressive strength values show that the inclusion of CHA in the cement matrix does not appreciably enhance the compressive strength of the sandcrete blocks. At 5% replacement of CHA the compressive strength is 2.16N/mm2, which is 15% less than the control value. Figure 2 revealed that there is decrease in compressive strength as the proportion of coconut husk ash increases in the mix. The reduction in compressive strength for the replacement is due to low percentage of Calcium Oxide and Silicate Oxide in coconut husk ash. These two silicates are the main constituent of cement and are mainly responsible for the strength development. So as the cement content is gradually replaced by the coconut husk ash, the quantity of cement for hydration is reduced thereby the strength of the sandcrete blocks is reduced. The Nigeria National Building Code (16) recommended that average strength of 6 sandcrete block shall be 2.00N/mm2 and lowest strength for individual block shall be 1.75N/mm2 sandcrete block (18). For the 5% replacement of CHA in the cement matrix, the least value for the 28th day compressive strength is 2.03N/mm2, higher than recommendation by the code. 3.2 Effect of CHA on Dry Density. There is inconsistency in the dry density of the mix for the ages, but the maximum dry density for all the ages occurred at 15% CHA replacement. The maximum value of 1945.90 Kg/m3 was recorded at 7 day test.
466
Proceedings of the 11th International Conference and 32nd Annual General Meeting of the Nigerian Institution of Agricultural Engineers (NIAE Ilorin 2011), October 17 – 20, 2011, Ilorin, Nigeria. ISBN: 978-036-578-8 Coconut Husk Ash as a Partial Replacement of Cement in Sandcrete Block Production Oyelade, O. A. (2011). Vol. 32: 465 – 469.
4. Conclusion The main conclusions derived from this investigation are as follows: 1. Agriculture wastes such as coconut husk ash does not show good pozzolanic property in the production of sandcrete blocks. 2. The maximum compressive strength of 2.16 N/mm2 was obtained for the sandcrete block specimens at a percentage CHA content of 5%. 3. Coconut husk ash addition should not exceed 5% of the weight of cement for best results. 4. The maximum compressive strength achieved at 5% is more than recommendation of 2.00N/mm2 recommended by Nigeria National Building Code (2006), for non load bearing wall. 5. As the percentage of CHA content in the mix increase the compressive strength decreased appreciably to a value of 0.06N/mm2at 30% CHA content. 6. There is no noticeable relationship between CHA content and dry density in the mix.
References Abdullahi M. (2005): “Compressive Strength of Sandcrete Blocks in Bosso and Shiroro Areas of Minna, Nigeria:. Civil Engineering Department, Federal University of Technology Minna, Niger State, Nigeria. BS 12 (1971): Portland cement (Ordinary and Rapid Hardening), Part 2, British Standards Institution, London National Building Code (2006), Federal Republic of Nigeria National Building Code First Edition. pp 319. Nimityongskul P. and Daladar T.U (1995), Use of coconut husk ash, corn cob ash and peanut shell ash as cement replacement, Journal of Ferrocement vol. 25, no1, pp. 35-44 (5 ref.) NIS 2000. NIS 87: (2000). Nigeria Industrial Standard: Standard for Sandcrete Blocks. Standard Organisation of Nigeria. Lagos, Nigeria. Oyekan G.L. (2007) ‘Crushed Waste Glass in Sandcrete Block Manufacture. Proceeding on 32nd Conference on Our World In Concrete And Structure:, Singapore pp 365-372 Oyekan G.L. (2008) ‘Effect of Admixture on the Compressive Strength of Sandcrete Blocks’. Journal of Engineering and Applied Sciences 3(6): 451-454. Table 1: Chemical Analysis result of Portland cement & Coconut Husk Ash Name of compounds Cement (%) CHA (%) Total Organic Content (Toc) 1.7 8.88 Calcium Oxide (Ca0.) 62.32 0.25 Silicate (Si02) 18.72 0.005 Aluminate (Al203) 6.2 5.10 Ferrite (Fe203) 0.94 2.48 Magnesium Oxide (Mg0) 1.62 0.09 Sulphur trioxide (S03) 1.1 0.12 Sodium oxide (Na20) 0.34 0.02
Table 2: Compressive Strength Test Result of Sandcrete block Specimens Containing Various CHA
467
Coconut Husk Ash as a Partial Replacement of Cement in Sandcrete Block Production Oyelade, O. A. (2011). Vol. 32: 465 – 469.
percentages. Percentage CHA Age content (Days) 7 0 14 21 28 7 5 14 21 28 7 10 14 21 28 7 15 14
Dry Density (kg/m3) 1,835.30 1,858.40 1,784.70 1,860.70 1,849.20 1,837.70 1,828.40 1,830.70 1,819.20 1,819.20 1,807.70 1,766.30 1,945.90 1,909.00
Compressive Strength at 28 days (N/mm2) 1.52 2.11 2.41 2.48 1.14 1.52 1.97 2.16 0.70 1.14 1.33 1.40 0.54 0.98
21
1,860.70
1.05
28
1,886.00
1.14
7
1,840.00
0.25
14
1,842.30
0.35
21
1,833.00
0.44
28
1,853.80
0.51
25
7
1,869.90
0.10
30
14 21 28 7 14 21 28
1,833.00 1,846.90 1,835.30 1,842.30 1,844.60 1,837.70 1,821.50
0.32 0.38 0.29 0.03 0.06 0.10 0.06
20
468
Proceedings of the 11th International Conference and 32nd Annual General Meeting of the Nigerian Institution of Agricultural Engineers (NIAE Ilorin 2011), October 17 – 20, 2011, Ilorin, Nigeria. ISBN: 978-036-578-8 Coconut Husk Ash as a Partial Replacement of Cement in Sandcrete Block Production Oyelade, O. A. (2011). Vol. 32: 465 – 469.
Figure 1: Plot of Compressive Strength against Percentage CHA content
Figure 2: Plot of Dry Density against Ages
469
